Method for a thermostable joining process

Abstract

The invention relates to a method for joining a first component (4) made of a first material and a second component (3) made of a second material, which differs from the first material, in a thermostable manner, wherein the first material has a greater thermal expansion coefficient than the second material. The first component (4) has a concavely tapering face (2), and the second component (3) has a face (1) with an opening which tapers convexly inwards and which is designed to complement the concavely tapering face (2) of the first component (3). A surface of the concavely tapering face (2) of the first component (4) and / or a surface of the face (1) of the second component (3) with an opening which tapers convexly inwards is provided with a joining agent for joining the first component (4) and the second component (3), and the concavely tapering face (2) is inserted into the complementary face (1) of the second component (3), a joint connection being formed by means of the joining agent.

Description

[0001] Process for thermostable joining

[0002] The present invention relates to a method for thermostable joining. Joints between dissimilar materials are often difficult to produce. For example, a reliable bond between a ceramic and a metal is very difficult to achieve, especially when exposed to a large temperature gradient. Although EP 0 629 596 B1 discloses a method for producing such a composite body, it requires internal soldering, which significantly limits the possible applications.

[0003] The present invention is therefore based on the object of proposing a method for thermostable joining in which the aforementioned disadvantages do not occur, ie with which a reliable connection between the joining partners can be produced even in the case of large temperature gradients.

[0004] This object is achieved according to the invention by a method according to the independent claim. Advantageous embodiments and further developments are described in the dependent claims.

[0005] In a method for the thermostable joining of a first component made of a first material and a second component made of a second material (wherein the second material is different from the first material and the first material has a larger thermal expansion coefficient than the second material), the first component has a concavely tapered side, while the second component has a side with a convexly inwardly tapered opening that is complementary to the concavely tapered side of the first component. A surface of the concavely tapered side of the first component and / oror a surface of the side with the convexly inwardly tapered opening of the second component is provided with a functional layer for joining the first component and the second component and the concavely tapered side of the first component is inserted into the complementarily formed side of the second component and a joining connection is carried out by means of the functional layer.

[0006] The specific design of the joining surface, either concavely tapered or convexly tapered inward, increases the joining surface area and achieves minimal absolute strain differences, thus minimizing thermal stresses. This significantly mitigates the trade-off between improved manufacturability and improved load-bearing capacity.

[0007] The method can provide for the first component to be made of a metallic material and / or the second component to be made of a ceramic material. Silicon nitride, SiSiX, silicon carbide, SiC, electro-porcelain, aluminum oxide, Al2O3, or zirconium oxide, e.g., ZrCh, can be used as the ceramic material. A steel such as the tempering steel 25CrMo4 can be used as the metal. However, one of the following steels can also be used: 41Cr4, 34CrMo4, 42CrMo4, 50CrMo4, 32CrMo2, 30CrMoV9, X45CrSi9-3+QTI, 29CrMoV9, ZlCrMoV9, 16MnCr5, or 48CrMoV6-7. Alternatively, glass can be used as a material instead of a ceramic material, i.e. an amorphous glass can be used instead of the crystalline ceramic material.

[0008] The functional layer can be designed either as a surface layer of the respective component or as a layer or coating applied externally to the respective component using a joining agent. In the case of a surface layer, the two components can be clamped together (and thus joined) by applying heat after contact. In particular, a reactive multi-layer system can be used as the surface layer, i.e. a layer system consisting of at least two materials applied one above the other in layers, which react in a self-propagating exothermic manner after exposure to activation energy, for example a brief increase in temperature. The resulting reaction heat can be used to melt a base material or a solder to create a joint. Nickel with aluminum or zirconium with silicon can be used as materials for such reactive multi-layer systems.

[0009] Adhesive can be used as the joining agent, but alternatively solder can also be used as the joining agent, with the joint being created by applying heat to the solder. When using the adhesive, heat can also be applied, although the joint can generally be formed without this heat application. What is usually a purely form-fitting connection when the concavely tapered side of the first component is inserted into the side of the second component that is complementary to this shape can thus be transformed into a force-fitting or material-fit joint using the joining agent. The joining agent also serves in particular to ensure local compensation of different expansions.

[0010] Typically, the first component has a hole in its concavely tapered side. This hole, which can be designed as a through hole or a blind hole, is usually arranged coaxially or parallel to the longitudinal axis of the first component or, in a cross-sectional view, is located centrally within the first component. The hole serves to improve internal load-bearing capacity during soldering or thermal loading.

[0011] It may be provided that the first component is used, with the surface of the concavely tapered side of the first component being formed as a body of revolution of a hyperbolic function, a polynomial function, or an exponential function. This provides a unique surface structure.

[0012] A ceramic component preferably has one side with a convex, inwardly tapered opening, thus corresponding to the second component. A metallic component can also have a concave, tapered side, thus corresponding to the first component. The ceramic component can already have the described shape as a green compact, resulting in manufacturing advantages in terms of machinability and cost.

[0013] The ceramic component and the metallic component can be joined, i.e. connected to each other, using the method described above.

[0014] By means of the method described above, a high-temperature turbocharger, a heat exchanger, an insulator and / or a compressor can thus preferably be produced from the first component and the second component.

[0015] Embodiments of the invention are illustrated in the drawings and are explained below with reference to Figures 1 to 5. They show:

[0016] Fig. 1 is a perspective view of a first component; Fig. 2 is a perspective view of a second component corresponding to Fig. 1;

[0017] Fig. 3 is a cross-sectional view of one end of the first component;

[0018] Fig. 4 is a cross-sectional view of one end of the second component corresponding to Fig. 3 and

[0019] Fig. 5 is a diagram of the expansion behavior of a device assembled from the first component and the second component.

[0020] Figure 1 shows a perspective view of a first component 4 which, in the present embodiment, is essentially cylindrical, although other shapes are also possible in further embodiments. One end of the first component 4 is in the form of a hexagon head screw head in the illustrated embodiment, but can also be cylindrical or have a different shape in further embodiments. A side opposite this end (or the end opposite along a longitudinal axis of the first component 4) is designed as a concavely tapered side 2, i.e. a surface of this concavely tapered side 2 of the first component 4 is designed as a body of revolution of a hyperbolic function, which can also be referred to as a concave cone. The first component 4 is made of a metallic material, in the illustrated embodiment a temperature-resistant heat-treated steel ora heat-resistant metal alloy with a thermal expansion coefficient of approximately 11.1*10. -6 K 1 In the illustrated embodiment, the length of the first component 4 is 95 mm, and the outer diameter is 24 mm. The concavely tapered side 2 tapers from a diameter of 24 mm over a length of 15 mm in the illustrated embodiment to a diameter of 3 mm.

[0021] Figure 2 shows a second component 3 in a view corresponding to Figure 1. Recurring features are provided with identical reference numerals in this figure as well as in the following figures. This second component 3 is also cylindrical, but on one side is designed in the form of the head of a hexagon screw, but in further exemplary embodiments it can also be cylindrical or in a different shape. A side 1 opposite this side, i.e. mathematically speaking one of the two circular intersection surfaces of the cylinder, is provided with an opening that tapers convexly towards the inside and is typically designed as a blind hole. The opening is designed such that it is complementary to the concavely tapered side 2 of the first component 4.Thus, when the concavely tapered side 2 of the first component 4 is inserted into this opening, a positive connection between the two components 3 and 4 would be created, which, however, would be releasable by a linear movement along the longitudinal axis of the components 3 and 4. The second component 3 is made of a ceramic material with a thermal expansion coefficient between 2.6 and 3.2*10. -6 K 1 Due to the different thermal expansion coefficients, joining ceramic and metal would result in a thermal expansion difference between the two joining partners under operating load or operating temperature. In the illustrated embodiment, the length of the second component 3 is 80 mm, with an outer diameter of 30 mm. The opening, which tapers convexly inward, tapers from a diameter of 24 mm over a length of 14.8 mm to a diameter of 3.4 mm in the illustrated embodiment.

[0022] Figure 3 shows a cross-sectional view of the concavely tapered end 2 of the first component 4, or rather, the concavely tapered side 2 of this component 4. A bore 6 formed as a blind hole is arranged centrally in the first component 4 and runs along the longitudinal axis of the first component 4. In the illustrated embodiment, the diameter of this bore is 1.5 mm. This bore 6 serves to improve the inward load-bearing capacity during a soldering process.

[0023] In a view corresponding to Figure 3, Figure 4 shows the end of the second component 3 provided with the opening 5, which is also designed as a blind hole. The opening 5 is also arranged parallel to the longitudinal axis in the second component 3. In further exemplary embodiments, the opening 5 may not be designed as a blind hole, but may extend along the longitudinal axis of the second component 3. To join the first component 4 and the second component 3, the surface of the concavely tapered side 2 and / or the surface of the convexly inwardly tapered opening in the exemplary embodiment shown in Figure 3 is provided with a joining agent as a functional layer, and the two components 3 and 4 are plugged together as shown on the right-hand side in Figure 5. An adhesive can be used as the joining agent, so that in this case a joint is preferably formed simply by plugging the two components 3 and 4 into one another.Alternatively, however, a solder can also be used as the joining agent, which must first be melted by the application of heat and then forms the joint. In further exemplary embodiments, a reactive multi-layer system can also be used as the functional layer, or a surface layer of the first component 4 is used as the functional layer instead of the joining agent, so that upon contact with the second component 3 and subsequent heating, a clamp is formed as a joint. The joined component shown in the right-hand part of Figure 5 can, for example, be used as a high-temperature turbocharger, heat exchanger, insulator or compressor. Typically, the joined component is used in applications in which a temperature gradient occurs along the longitudinal axis of the component, i.e. one side of the component has a higher temperature than the other side of the component opposite this side.

[0024] As shown in the left part of Figure 5, due to the special shape in the joined state along the longitudinal axis across the radius of the joined component, lower expansion forces are measured when the temperature gradient shown is applied compared to a purely conical design or a design with an outwardly curved surface. Thus, due to the joining design, a thermostable or material-adapted ceramic-metal connection is achieved. The length of the arrows indicates the magnitude of the radial expansion. In other words, a strain-adapted high-temperature joint design is enabled.

[0025] The described method compensates for the critical radial strain for the ceramic material. The surface area of ​​the joint can be described by the formula Y=(A / (x-xo))+yo, where Y is the height, A the local gradient, xo the vertical asymptote (the radius), and yo the y-shift of the function. Only features of the various embodiments disclosed in the exemplary embodiments can be combined with one another and claimed individually.

Claims

Patent claims 1. A method for the thermostable joining of a first component (4) made of a first material and a second component (3) made of a second material different from the first material, wherein the first material has a larger thermal expansion coefficient than the second material, and wherein the first component (4) has a concavely tapered side (2) and the second component (3) has a side (1) with a convexly inwardly tapered opening which is complementary to the concavely tapered side (2) of the first component (3),wherein a surface of the concavely tapered side (2) of the first component (4) and / or a surface of the side (1) with the convexly inwardly tapered opening of the second component (3) is provided with a functional layer for joining the first component (4) and the second component (3), and the concavely tapered side (2) is inserted into the complementary side (1) of the second component (3), and a joining connection is formed by means of the functional layer.

2. Method according to claim 1, characterized in that the first component (4) is formed from a metallic material.

3. Method according to claim 1 or claim 2, characterized in that the second component (3) is formed from a ceramic material.

4. Method according to one of the preceding claims, characterized in that a surface layer of the first component (4) or of the second component (2), in particular a reactive multi-layer system, or a joining agent is used as the functional layer.

5. The method according to any one of claims 1-4, characterized in that an adhesive or a solder is used as the joining agent, wherein, when using the solder, the joining connection is made by applying heat to the solder.

6. The method according to any one of the preceding claims, characterized in that the first component (4) has a bore (6) in its concavely tapered side (2).

7. Method according to one of the preceding claims, characterized in that the first component is used, wherein the surface of the concavely tapered side of the first component (4) is used as Rotation body of a hyperbolic function is formed.

8. Ceramic component (3) with one side having a convex inwardly tapered opening.

9. Metallic component (4) with a concavely tapered side.

10. High-temperature turbocharger, heat exchanger, insulator or compressor with a first component (4) and a second component (3) joined by the joining method according to claim 1.

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